Field of the Invention
The present invention relates to a stator molded with a resin.
Background
Conventionally, a stator molded with a resin is sometimes provided in, for example, a brushless DC motor so as to protect the stator. As disclosed in Japanese Patent Laid-Open No. 2001-258186, an annular core formed by bending a straight stacked core is known as a core of the stator molded with a resin. The annular core, around which a winding is wound, is maintained in an annular shape in a mold, and further molded with a resin in the mold. At the time of molding, a core metal is inserted into an inner side of a plurality of teeth of the annular stator. A region other than distal end surfaces of the teeth is thereby covered with the resin.
However, a joint that exists at a bent position of the core has a low rigidity. Thus, when the resin is injected into the mold, the shape of the annular core may be slightly deformed upon receiving a force from a resin flow. When a circularity of the core or a pitch uniformity of the teeth is reduced, or a concentricity of the stator to a rotating section is deteriorated due to the deformation of the core, motor vibrations are increased.
Meanwhile, in Japanese Patent Laid-Open No. 2004-312790, an engagement recess is provided in each of centers of distal end portions of all teeth, and an engagement projection is also provided on an outer periphery of a core metal. When the core metal is inserted into an annular core, the engagement projection engages with the engagement recess. Accordingly, a pitch of the plurality of teeth is maintained at a predetermined interval when a resin is injected into a mold. An inner diameter of the teeth is also retained.
However, when all the teeth are engaged with the projections of the core metal as in the method of Japanese Patent Laid-Open No. 2004-312790 or the like, it takes time to assemble an assembly in which the core is arranged around the core metal. Alternatively, an extra jig or the like for facilitating assembling is required, or a skilled worker is required for assembling.
At least an embodiment of the present invention ensures the shape of a core without deteriorating workability when manufacturing a resin molded stator.